1. Technical Field of the Invention
The present invention relates to a vehicle rotating electrical machine mounted on vehicles such as passenger cars or trucks, and in particular, to a cap structure of a pulley unit for the vehicle rotating electrical machine.
2. Related Art
As one example of the related art, a pulley unit with an integrated one-way clutch, which is able to be mounted in auxiliary machines for a vehicle, has been known (see, e.g., JP-A-2003-004121). In this pulley unit, a polygonally-shaped hole portion is formed so as to open on an axial end surface of a rotor shaft. In the hole portion, a jig for attachment is fitted so as to attach the rotor shaft to the auxiliary machine for the vehicle.
As the other example of the related art, a pulley unit with an integrated one-way clutch, which is mounted in a rotating electrical machine for a vehicle, has been also known (see, e.g., JP-A-2011-045170). This pulley unit is configured to perform at least one of transmission and reception of a rotation drive force to and from a rotation shaft of a rotor. The pulley unit includes a cap attached to an opening portion formed on an axial front end of the pulley unit. When the cap is attached to the pulley unit, internal pressure of the pulley unit increases. In order to reduce the internal pressure, an air passage is formed so as to ventilate an internal space of the pulley unit closed by the cap.
In the pulley unit disclosed in JP-A-2003-004121, due to moisture or water, rust may occur on an end face and inner face of the polygonally-shaped hole portion which is a an exposed portion of metal, thereby decreasing value of the vehicle (i.e., aesthetic appearance of surrounding part of an engine). In general, a rust prevention process such as an antirust coating is implemented for the exposed portion of metal, which makes it possible to suppress occurrence of rust.
If the rust prevention process is performed for the exposed portion of metal in the pulley unit, a coating material etc. can be attached to a seal of a bearing of the pulley unit, which makes it difficult to implement the rust prevention process for a local portion avoiding the seal and a concave surface of the polygonally-shaped hole portion. For these portions, the rust prevention process requires more man-hours (time and effort). However, this is impractical because costs are significantly increased.
The rust prevention process may be performed for a pulley shaft itself which is in a state before the seal is provided therein. In this case, coating material may be accidentally removed in the subsequent assembly process. The rust prevention process is required to be performed after the pulley unit is mounted on the accessory, in order to obtain sufficient effect thereof.
In the structure disclosed in JP-A-2011-045170, the cap is attached to the pulley unit and then an inside of the pulley unit is unexposed. This is effective in maintaining aesthetic appearance of the pulley unit. When the cap is attached to the pulley unit, the internal pressure is decreased, and then, the cap is needed to be assembled with high accuracy in order to maintain high level of air tightness. On attachment of the cap, an outer pulley of the pulley unit may be subjected to excessive loading which adversely affects the clutch mechanism inside the pulley unit. In order to avoid this situation, dedicated equipment for attaching the cap is required, and management of an assembly process becomes more complicated, which leads to an increase in cost.